Human placental membrane (e.g. amniotic membrane or tissue) has been used for various types of reconstructive surgical procedures since the early 1900s. The membrane serves as a substrate material, more commonly referred to as a biological dressing or patch graft. Such membrane has also been used widely for ophthalmic procedures in the United States and in countries in the southern hemisphere. Typically, such membrane is either frozen or dried for preservation and storage until needed for surgery.
Such placental tissue is typically harvested after an elective Cesarean surgery. The placenta has two primary layers of tissue including amniotic membrane and chorion. The amniotic membrane is a non-vascular tissue that is the innermost layer of the placenta, and consists of a single layer, which is attached to a basement membrane. Histological evaluation indicates that the membrane layers of the amniotic membrane consist of epithelium cells, thin reticular fibers (basement membrane), a thick compact layer, and fibroblast layer. The fibrous layer of amnion (i.e., the basement membrane) contains cell anchoring collagen types IV, V, and VII. The chorion is also considered as part of the fetal membrane; however, the amniotic layer and chorion layer are separate and separable entities.
Amniotic membrane and chorion tissue provide unique grafting characteristics when used for surgical procedures, including providing a matrix for cellular migration/proliferation, providing a natural biological barrier, are non-immunogenic, promote increased self-healing, are susceptible of being fixed in place using different techniques including fibrin glue or suturing. And, such grafts, when properly prepared, can be stored at room temperature for extended periods of time, without need for refrigeration or freezing, until needed for a surgical procedure.
Known clinical procedures or applications for such amnion grafts include Schneiderian Membrane repair (i.e. sinus lift), guided tissue regeneration (GTR), general wound care, and primary closure membrane. Known clinical procedures or applications for such chorion grafts include biological wound dressing.
A detailed look at the history and procedure for harvesting and using “live” amniotic tissue for surgical procedures and a method for harvesting and freezing amniotic tissue grafts for ophthalmic procedures is described in U.S. Pat. No. 6,152,142 issued to Tseng, which is incorporated herein by reference in its entirety.
There is a need for improved procedures for harvesting, processing, and preparing amnion and/or chorion tissue for later surgical grafting procedures.
There is a need for improved procedures for processing and preparing multiple layers of amnion and/or chorion tissue for later surgical grafting procedures.
There is a need for preparing and storing such tissue such that the stroma and basement sides of the tissue are easily and quickly identifiable by a surgeon when using such tissue in a surgical procedure.
For these and many other reasons, there is a general need for a method for preparing placenta membrane tissue grafts for medical use, and that includes the steps of obtaining a placenta from a subject, cleaning the placenta, separating the chorion from the amniotic membrane, disinfecting the chorion and/or amniotic membrane, mounting a selected layer of either the chorion or the amniotic membrane onto a drying fixture, dehydrating the selected layer on the drying fixture, and cutting the selected layer into a plurality of tissue grafts. There is an additional need for a drying fixture that includes grooves or raised edges that define the outer contours of each desired tissue graft and that make cutting of the grafts more accurate and easy. There is a further need for a drying fixture that includes raised or indented logos, textures, designs, or text that emboss the middle area of the tissue grafts during dehydration and that enables an end user to be able to distinguish the top surface from the bottom surface of the graft, which is often necessary to know prior to using such grafts in a medical application or surgical procedure. Such logos, textures, designs, or text can be used for informational purposes or they can, additionally and advantageously, be used for marketing or advertising purposes. There is a need for grafts that are comprised of single layers of amnion or chorion, multiple layers of amnion or chorion, or multiple layers of a combination of amnion and chorion.
The present invention meets one or more of the above-referenced needs as described herein in greater detail.